Black smoke eliminating device for internal combustion engine and exhaust gas cleaning system including the device

ABSTRACT

The temperatures of exhaust gas streams into a black smoke eliminating device are uniformly raised to assuredly burn and eliminate the black smoke at the black smoke eliminating device. Accordingly, the restoration of the black smoke eliminating device is uniformly carried out while avoiding melt damage of the filter. Further, the exit temperature of the black smoke eliminating device is descended by a simple device of lower cost. For accomplishment of the present objects, the heating device and black smoke eliminating device are provided in a plural and divided manner and there are provided a baffle member and a space portion, to thereby equalize the volume quantities and temperatures of exhaust gas flows flowing into these devices. Further, the fuel is atomized into fine particles by injection into pressurized air and the obtained mixture is uniformly mixed into the exhaust gas, so that there are uniformly raised the temperatures of exhaust gas streams into the black smoke eliminating device. The temperature of exhaust gas is descended by a simple structure of porous body disposed downstream of the black smoke eliminating device.

FIELD OF THE INVENTION AND RELATED ART STATEMENT

The present invention generally relates to an exhaust gas cleaningsystem for cleaning exhaust gas from an internal combustion engine suchas diesel on engine and gas turbine, and particularly relates to a blacksmoke eliminating device for trapping and eliminating the black smokefrom the exhausted gas and to an exhausted gas cleaning system includingthe device.

In the field of internal combustion engines, particularly dieselengines, the black smoke in the exhausted gas is becoming a subject ofregulations, so that a variety of techniques have been proposed toeliminate the black smoke.

Conventionally, as a filter for eliminating the carbonaceous black smokefrom exhaust gas in an internal combustion engine, there have beenmainly adopted the honeycomb types of porous ceramic structures made ofcordierite material which has excellent heat resistance and thermalshock resistance. However, in this type of filter, a phenomenon calledloading occurs as the quantity of trapped black smoke increases.Therefore, it becomes necessary to detect such loading by a detectingmeans such as an exhaust gas pressure sensor, in order to carry out arestoration treatment such as combustion or back washing of the filter.

On the other hand, in the Japanese Patent Application Laid-OpenPublication No.5-44435(44435/1993) is disclosed one of the conventionaltechniques for forcibly burning or oxidizing the exhaust gas of internalcombustion engines. In this technique, fuel is introduced into theexhaust gas of a diesel engine as internal combustion engine, andthereafter agitated and mixed by means of a turbo-charger. Further, thethus obtained mixture is burnt or oxidized within a downstream filter byan oxidation catalyst carried thereby, so that the black smoke trappedby the filter is burnt by the heat generated by the burning of themixture.

OBJECT AND SUMMARY OF THE INVENTION

The conventional technique as disclosed in the aforementioned Laid-OpenPublication is however not applicable to those engines which do not havea turbo charger. Still less, this technique fails to address theheat-resistant characteristic of the oxidation catalyst. That is, thepermissible quantity of trapped black smoke to be burnt for restorationhas a close relation to the highest burning temperature within thefilter. Thus, there is typically determined an upper limit in thequantity of black smoke trapped within the filter such that the burningtemperature thereof does not exceed the heat-resisting temperature ofthe filter. However, oxidation catalysts represented by noble metalshave their heat-resisting temperatures in the range of 500° C. to 900°C. whereas such filter materials as cordierite have their heat-resistingtemperatures higher than 1,000° C. Therefore, the oxidation catalystsnecessarily deteriorate with the heat generated by the burning of theblack smoke. Consequently, the exhaust gas is likely to be exhaustedwith the mixed fuel remaining unburnt, as the number of times therestoration is carried out on the oxidation catalyst increases.

Concerning the above, it is possible to limit the quantity of blacksmoke to be burnt in each restoration treatment in view of theheat-resisting characteristic of oxidation catalyst. However, suchlimitation is practically disadvantageous, because the restoration cyclethen becomes shorter and the fuel efficiency becomes low.

Further, when materials having a low thermal conductivity such ascordierite are used or when the burning reaction rate within the filteris not satisfactorily large relative to the flow rate of exhaust gas,the heat generated by the burning will be transferred to downstream ofthe filter so that the filter temperature is not effectively raised thusthe fuel is likely to be consumed in an increased quantity.

Therefore, it is a first object of the present invention to provide ablack smoke eliminating device for an internal combustion engine whichis capable of solving the problems as noted above.

In addition, there exist the following points to be improved, in casethat the heating device and the filter are disposed upstream anddownstream, respectively, in a divided manner as in the above notedconventional technique.

Namely, referring to FIG. 10, there is shown an example of a device foreliminating black smoke in exhaust gas of an internal combustion engine1 such as diesel engine. There are provided an exhaust pipe 11 forflowing exhaust gas from the engine 1, a heating device 3 for heatingthe exhaust gas, and a filter 4 for trapping the black smoke.

In the conventional exhaust gas cleaning or purifying system asconstructed above, the exhaust gas from the engine 1 flows via the pipe11 into the heating device 3, where the gas is occasionally heated to araised temperature for allowing the black smoke to burn, and led intothe filter 4. The black smoke trapped by the filter 4 burns because ofthe heat of the exhaust gas having elevated temperatures, so that thefilter 4 is restored.

In case that the black smoke in the exhaust gas is eliminated by theblack smoke eliminating device and then the restoration is effected onthe device as well as the related components, the capacity of theheating device 3 for heating the exhaust gas and the filter 4 fortrapping the black smoke has to be increased, as the exhaust gas fromthe engine increases in quantity. However, because such restrictions asthose for manufacturing are imposed on the heating device 3 and thefilter 4, these device and filter are divided into a plurality ofcomponents arranged in parallel with the exhaust gas flow.

Then such a problem arises that exhaust gas streams through theplurality of heating devices 3 tend to become uneven, in case of theconventional exhaust gas cleaning system as shown in FIG. 10. Also,temperatures of exhaust gas streams flowing through the plurality of theblack smoke trapping filters 4 are not uniform among all the filters.

Therefore, it is a second object of the present invention to provide anarrangement of plurality of black smoke eliminating devices andplurality of heating devices which allows even flow of exhaust gas amongthe heating devices. At the same time, the temperatures of exhaust gasflowing into the black smoke eliminating devices are adjusted to becomeuniform, even when a plurality of these devices are arranged in parallelto each other, corresponding to increasing displacement volumes of theengines.

Referring to FIG. 11, there is shown another example of an exhaust gascleaning system including a black smoke eliminating device. In thissystem, there is additionally provided a fuel supply device 2 forinjecting the fuel into the exhaust pipe 11 in which the exhaust gas isflowing from the internal combustion engine 1, so that the temperatureof exhaust gas is raised by virtue of the injection of fuel.

That is, the exhaust gas containing the injected fuel is introduced intoheating device 3 of oxidation catalyst convertor type and heated by theheat of oxidation caused by the catalyst. The exhaust gas is then fed tothe black smoke trapping filter 4. Then, the black smoke trapped by thefilter 4 is burnt by the exhaust gas having raised temperatures.

In case of the system shown in FIG. 11 where the temperature of exhaustgas is raised by the injection of fuel, it is difficult to atomize thefuel into fine particles, and the fuel fails to equally disperse withinthe exhaust pipe, resulting in an uneven mixture of the exhaust gas andfuel. Thus, the restoration of the black smoke trapping filter 4 willoccur only partially and the injected fuel may be eventually exhaustedunburnt, also the filter 4 may be damaged by partial melting.

Thus, it is a third object of the present invention to provide a blacksmoke eliminating device having a remarkably improved restorationefficiency by atomizing the fuel into sufficiently fine particles so asto disperse the fuel uniformly into the exhaust gas when the fuel isinjected into the exhaust gas for elevating the temperature of theexhaust gas with this device, the eventual exhaustion of unburnt fuel,overheat and melt damage of the filter which may be caused if the fuelis unevenly dispersed can be avoided.

Shown in FIG. 12 is yet another example of an exhaust gas cleaningsystem including a black smoke eliminating device. In this example,there is provided a means for cooling the exhaust gas, because it isdisadvantageous from the safety standpoint of view to discharge theexhaust gas into the atmosphere with the temperature of the gas havingbeen raised for burning the black smoke.

In FIG. 12, the exhaust gas from the internal combustion engine 1 isintroduced via the exhaust pipe 11 into the heating device 3 such as anoxidation catalyst type convertor and heated, and thereafter led intothe filter 4 to burn the trapped black smoke. The exhaust gas of hightemperature, the black smoke of which has been eliminated by the filter4, is then fed to an air-cooled cooling device 8 and cooled to a lowertemperature, and then discharged out.

When an air-cooled of cooling device is to be provided to lower thetemperature of exhaust gas for the elimination treatment of black smoketherein as shown in FIG. 12, the aimed effect will be achieved. However,the structure of cooling device disadvantageously becomes complicatedand large in size, leading to cost increases.

It is hence a fourth object of the present invention to provide anexhaust gas cleaning system including a cooling device which has asimple and compact structure with lower costs but capable of cooling theexhaust gas to lower its temperature upon the elimination treatment ofblack smoke.

The black smoke eliminating device for an internal combustion engine,according to the first aspect of the present invention for attaining thefirst object thereof, is characterized by comprising a filter fortrapping the black smoke in exhaust gas, the filter being disposeddownstream from an exhaust gas exit of the engine, a fuel introducingmeans for introducing fuel into the exhaust gas, the fuel introducingmeans being disposed upstream of the filter, and an oxidation catalystfor oxidizing the fuel, the catalyst being disposed upstream of thefilter.

The aforementioned problems are solved by the exhaust gas cleaningdevice according to the present invention, and the second aspect thereoffor attaining the second object is an improvement in an exhaust gascleaning system having a heating device for heating the exhaust gas froma thermal engine such as an internal combustion engine, and a blacksmoke eliminating device for eliminating the black smoke from theexhaust gas which is to be heated by said heating device, theimprovement comprising the heating device and the eliminating device areeach divided into a plurality of devices arranged perpendicularly to aflow direction of the exhaust gas, so as to provide divided heatingdevices and divided black smoke eliminating devices, and a baffle memberfor regulating exhaust gas flow and disposed upstream of the dividedheating devices, and a space portion defined in the upstream of thedivided black smoke eliminating devices.

The third aspect for attaining the third object is an exhaust gascleaning system having a heating device for heating the exhaust gas inan exhaust pipe from a thermal engine such as internal combustionengine, and a black smoke eliminating device for eliminating the blacksmoke from the exhaust gas which is heated by the heating device, thesystem being g characterized by further comprising a fuel supply devicefor supplying the fuel into the exhaust gas, the fuel supply devicebeing disposed on the exhaust pipe at an upstream position from theblack smoke eliminating device, and a fuel mixing device for mixing thefuel supplied from the supply device with the exhaust gas, the mixingdevice being disposed in the exhaust pipe at an upstream position of theblack smoke eliminating device, and the mixing device comprising aplurality of partition plates disposed along the exhaust gas flow atpredetermined intervals and each formed with a through hole for passingtherethrough the exhaust gas to form a turbulent flow.

The fourth aspect for attaining the third object is that in the thirdmeans the heating device comprises an oxidation catalyst convertor, andthe fuel mixing device is disposed in the exhaust pipe at an upstreamposition from the oxidation catalyst convertor.

The fifth aspect for attaining the third object is an exhaust gascleaning system having a heating device for heating the exhaust gas inan exhaust pipe from a thermal engine such as internal combustionengine, and a black smoke eliminating device for eliminating the blacksmoke from the exhaust gas which is to be heated by the heating device,the system being characterized by further comprising a pressurized airsupply device for supplying pressurized air, a fuel injection device forinjecting the fuel into the pressurized air to thereby atomize the fuel,the fuel injection device being disposed on the exhaust pipe at anupstream position from the black smoke eliminating device, and a mixedfluid injection device for mixing the injected fuel with the pressurizedair and for injecting the thus mixed fluid into the exhaust pipe, thefluid injection device being disposed on the exhaust pipe at an upstreamposition from the black smoke eliminating device.

The sixth and seventh aspects for attaining the third object arecharacterized, in the system according to the fifth aspect, that theheating device comprises an oxidation catalyst convertor, and the mixedfluid injection device is disposed on the exhaust pipe at an upstreamposition from the oxidation catalyst convertor, or wherein the fuelinjection device comprises a fuel pump for pressurizing the fuel from afuel tank and feeding the pressurized fuel, a fuel regulator forregulating the pressure of the pressurized fuel fed from the fuel pump,and an injector for injecting the pressurized fuel of a regulated flowrate from the regulator into the pressurized air.

The eighth aspect for attaining the fourth object of the presentinvention is an exhaust gas cleaning system having a heating device forheating the exhaust gas in an exhaust pipe from a thermal engine such asinternal combustion engine, and a black smoke eliminating device foreliminating the black smoke from the exhaust gas which is to be heatedby the heating device, the system further comprising a porous body fordescending the temperature of the exhaust gas, the porous body havingmultiple through holes for passing therethrough the exhaust gas andbeing disposed in the exhaust pipe at an downstream position from theblack smoke eliminating device.

In the eighth aspect porous body preferably consists of a ceramicmaterial.

According to the first aspect of the present invention, the means forintroducing the fuel into the exhaust gas and the oxidation catalyst forburning the fuel acting as a heating means are disposed upstream of thefilter in a separated manner therefrom. Thus, the oxidation catalyst isnormally operable at a temperature below its heat-resisting temperaturewithout the heat of combustion affecting at the filter, so that thedeterioration of the catalyst can be restrained effectively. Further,the heat loss toward the downstream of the filter is restricted to asmall extent by virtue of the thermal insulation of the filter itself,so that the heat of combustion of fuel can be effectively utilized forraising the temperature of the filter, leading to a further reduction offuel consumption as compared to the prior art.

According to the second aspect of the present invention, the exhaust gasis uniformly distributed into the divided type of heating device by thebaffle member. Further, the streams of exhaust gas as heated by theplurality of heating devices thus having possible temperaturefluctuations do flow into the space portion to be mixed therein forequalizing their temperatures, and thereafter flow into the black smokeeliminating device. Thus, the plurality of black smoke eliminatingdevices receive the uniform flow rates and uniform temperatures ofexhaust gas streams, so that there can be effectively attained therestoration of the devices by means of combustion elimination of blacksmoke, while advantageously dealing with an increase of flow volume ofexhaust gas.

Further, according to the third and fourth aspects of the presentinvention, there is formed a turbulent flow of exhaust gas by means ofpartition plates so that the fuel is uniformly mixed into the exhaustgas and fed to the black smoke eliminating device. Consequently, theblack smoke in the black smoke eliminating device uniformly burns sothat overheating and melt damages of this device due to unevendispersion of fuel, if any, can be avoided.

Still further, according to the fifth to seventh aspects of the presentinvention, the fuel is atomized by the fuel injection device into fineparticles and thereafter mixed with the pressurized air, followed bymixing thereof with the exhaust gas by the mixed fluid injection device,so that the vaporization of fuel is effectively promoted. The exhaustgas containing therein the uniformly mixed fuel is heated by the heatingdevice and thereafter fed to the black smoke eliminating device, so thatthe restoration thereof is performed at a higher efficiency whileavoiding overheat and melt damage of the black smoke eliminating devicedue to uneven dispersion of fuel if any.

Yet further, according to the eighth aspect of the present invention,the exhaust gas passes through the through holes of the porous bodydisposed downstream of the black smoke eliminating device, so that thesensible heat of exhaust gas is absorbed and backwardly radiated to theupstream of the body. Thus, the temperature of exhaust gas becomes loweron the downstream side of the black smoke eliminating device. Theexhaust gas is accordingly cooled by means of such an uncomplicated andcompact construction of low cost that the porous body is simply disposeddownstream of the black smoke eliminating device.

The above and further objects, features, details and advantages of thepresent invention will become apparent from the following detaileddescription of preferred embodiments of the invention when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a whole of black smoke eliminating deviceaccording to the first embodiment of the present invention;

FIG. 2 is a flow chart of the operation for restoring the filter in thefirst embodiment;

FIG. 3 is a systematic view of an exhaust gas cleaning system for aninternal combustion engine according to the second embodiment of thepresent invention;

FIG. 4 is a systematic view of an exhaust gas cleaning system for aninternal combustion engine according to the third embodiment of thepresent invention;

FIG. 5 is a structural view of a fuel mixing device in the thirdembodiment;

FIG. 6 is a view, corresponding to FIG.4, of the fourth embodiment ofthe present invention;

FIG. 7 is a systematic view of an exhaust gas cleaning system for aninternal combustion engine according to the fifth embodiment of thepresent invention;

FIG. 8 is a diagram for showing a temperature transition in the fifthembodiment;

FIG. 9 is a diagram for showing a temperature transition of exhaust gasin the fifth embodiment;

FIG. 10 is a systematic view of the conventional exhaust gas cleaningsystem (first example);

FIG. 11 is a systematic view of the conventional exhaust gas cleaningsystem (second example); and

FIG. 12 is a systematic view of the conventional exhaust gas cleaningsystem (third example).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The first embodiment according to the present invention will bedescribed hereinafter with reference to FIGS. 1 and 2. FIG. 1 is aschematic view of a whole of this embodiment. In the internal combustionengine (not shown), there is provided a metal casing 75 containingtherein an oxidation catalyst 25 and a ceramic filter 26. The catalyst25 is disposed upstream and has a honeycomb or foamed structure, whilethe filter 26 is disposed downstream and has a structure such ashoneycomb. There is ensured the airtightness and thermal insulation forcatalyst 25 and filter 26 with respect to the metal casing 75, by meansof thermally expandable ceramic seals.

In the upstream of the catalyst 25 is arranged an exhaust system 24which includes a nozzle 27 for injecting a liquid fuel such as gas oilfed from a pump 71 within a fuel tank 30 for the liquid fuel. Betweenthe nozzle 27 and catalyst 25 is disposed a vaporizing mixer mechanism76 such as piled stainless steel meshes or mixer for rendering the fuelinjected by the nozzle 27 be effectively vaporized by the exhaust gasand then be mixed therewith.

In the upstream of the oxidation catalyst 25 within the casing 75, thereis provided a back pressure sensor 28 for detecting the loading of thefilter 26. Further, in the downstream of the filter 26, there isprovided a temperature sensor 29 for monitoring the burning state of theblack smoke.

The signals from the sensors 28 and 29 and that from a detecting means72 for detecting the rotational speed of the engine are fed to a controlcircuit 73. This circuit 73 controls the solenoid valves (not shown)with respect to their distances between opening and closing portion anddurations of opening and closing actions, which valves are disposedinternally of the nozzle 27 and a regulator means 74, respectively,which regulator means 74 regulates the pressure of fuel fed from thetank 30 via pump 71.

The operation of this embodiment will be described hereinafter withreference to the flow chart shown in FIG. 2. When the loading of thefilter 26 is detected by the back pressure sensor 28, the signal thereofis fed to the control circuit 73. The circuit 73 then controls thenozzle 27 and regulator means 74 such that the nozzle 27 injects fuel ofan amount to be predetermined in response to the rotational speed ofengine which is detected by the detecting means 72. In other words, thepressure of fuel to be fed from the tank 30 by means of pump 71 isregulated to a constant value by virtue of the regulator opening anglethe distance between opening and closing portion and the duration ofopening and closing actions of the solenoid valve in the nozzle 27 areprecisely controlled by the control circuit 73, thus the quantity offuel to be injected is precisely controlled.

In the above, the fuel in the exhaust gas is vaporized and further mixedtherewith by means of the vaporizing mixer mechanism 76 so that theexhaust gas becomes a rarefied combustible gas at the downstream of thevaporizing mixer mechanism 76. This combustible gas is catalyticallyoxidized or burnt at a low temperature by the oxidation catalyst 25, andthe heat of combustion generated thereby causes the black smoke astrapped by filter 26 to be burnt thus eliminated. At this time, it isnecessary to avoid the melt damage of the filter 26 due to anexcessively raised temperature. To this end, when the temperature ofexhaust gas as detected by the temperature sensor 29 exceeds apredetermined upper limit value, the signal representative thereof isfed to the control circuit 73 to stop the injection of fuel. The filter26 is restored in such a manner as described above, and the continuoustrapping of black smoke can be of course performed even during therestoring operation.

In this embodiment, the liquid fuel is vaporized and mixed with theexhaust gas by means of the vaporizing mixer mechanism 76 disposedupstream of the filter 26, and the exhaust gas is burnt at a lowtemperature at the catalyst 25 disposed upstream of the filter 26. Thus,the catalyst 25 is operated at a temperature lower than itsheat-resisting temperature without any affection due to heat ofcombustion at the filter 26 disposed downstream, so that never will thecatalyst 25 be deteriorated. Further, while there is burnt the blacksmoke as trapped by the filter 26 disposed downstream, the heat losstoward the downstream of the filter 26 can be restricted to a smallextent by virtue of the thermal insulation effect of the filter 26itself. Thus, the heat of combustion of fuel can be effectively utilizedfor raising the temperature of the filter 26, leading to a quantitativereduction of fuel consumption.

There will be described hereinafter further embodiments of the presentinvention, with reference to FIGS. 3 to 9.

Shown in FIG. 3 is an exhaust gas cleaning system for an internalcombustion engine according to the second embodiment of the presentinvention.

In FIG. 3, this system includes the heating device 3 for heating exhaustgas from the exhaust pipe 11 connected to the internal combustion engine1 such as diesel engine, and the black smoke trapping filter 4 fortrapping the black smoke in the exhaust gas.

The heating device 3 and the black smoke trapping filter 4 are providedin a plural and divided manner perpendicularly to a flow direction Z ofexhaust gas, so as to provide a divided type of heating device and adivided type of black smoke eliminating device, corresponding to anincrease of the displacement volume of the engine. In detail, theheating device 3 comprises three pieces of heating devices 31, 32 and 33whereas the filter 4 comprises three pieces of black smoke trappingfilters 41, 42 and 43. Although the division number for these components3 and 4 is "three" here, it is of course possible to appropriately adoptanother number in view of the characteristics of the components.

In the upstream of the plurality of heating devices 31, 32 and 33, thereis disposed a baffle member 6 for regulating the exhaust gas stream Z.Further, there is defined a predetermined volume of space portion 5between the heating device 3 and the filter 4.

There will be described hereinafter the operation of the secondembodiment shown in FIG. 3. Firstly, the exhaust gas flow Z from theengine 1 is uniformly dispersed with respect to a section perpendicularto its flow direction by the baffle member 6, and thereafter uniformlyflows into heating devices 31, 32 and 33. Thus, the exhaust gas isuniformly distributed into the heating devices 31, 32 and 33.

The streams of exhaust gas are then to be heated to a predeterminedtemperature in each of the heating devices 31, 32 and 33, where mayoccur a fluctuation between the heated temperatures of streams due tosome reason such as capacities of the devices. Nonetheless, the streamswill then flow into the predetermined volume of the space portion 5 tobe mixed with one another so that their temperatures should be equalizedthere. The exhaust gas is then introduced into the black smoke trappingfilters 41, 42 and 43, at which the black smoke is trapped to be burnt.Thus, the exhaust gas is exhausted into the atmosphere, in a cleanedcondition.

As described above, each of the heating devices 31, 32 and 34 receives auniform quantity of exhaust gas stream by means of the baffle member, sothat the devices will operate effectively. In addition, the streams fromthese devices are equalized in temperature through the space portion 5before flowing into each of the black smoke trapping filters 41, 42 and42, so that the restoration of the filter 4 is effectively carried out.

The exhaust gas cleaning system according to the third embodiment of thepresent invention is shown in FIGS. 4 and 5.

As shown in FIG. 4, this system includes the fuel supply device 2 forinjecting the fuel into the exhaust pipe 11 in which the exhaust gas isflowing from the internal combustion engine 1 toward the black smoketrapping filter 4 via a fuel mixing device 7 and the oxidation catalystconvertor type of the heating device 3 for heating the fuel mixedexhaust gas from the mixing device 7 by the oxidation heat.

Referring to FIG. 5, the mixing device 7 comprises a plurality ofpartition plates 67 each formed with a through hole 81, and disposed atpredetermined intervals along the exhaust gas flow Z. These holes 81 aredivergently positioned in the circumferential or radial direction of theplates 67, so as to hasten the vertical flow of the exhaust gascontaining fuel therein.

There will be described below the operation of the third embodiment.

The mixing device 7 receives the exhaust gas Z containing the fuel whichis injected by the fuel supply device 2. This exhaust gas Z will thenpass through the alternately positioned holes 81 of plates 67 to form avertical flow, whereby the fuel is uniformly mixed into the exhaust gasZ.

This exhaust gas Z containing fuel is then introduced into the oxidationcatalyst convertor 3 shown in FIG. 4 to be heated there by the oxidationheat of the fuel, and thereafter fed to the black smoke trapping filter4 so as to burn the black smoke trapped thereby. Consequently, thefilter 4 is restored.

FIG. 6 shows an exhaust gas cleaning system for an internal combustionengine according to a fourth embodiment of the present invention.

In FIG. 6, this system includes a fuel tank 19 for fuel 53, a fuel pump18, a fuel regulator 17 for regulating the pressure of the fuel to apredetermined value, and an injector 16 for injecting the fuel into aninjection nozzle 15 which will be explained below. The fuel 53 in thetank 19 is fed to the injector 16 via the fuel regulator 17, by thefunction of the pump 18.

There are further provided an air pump 10 for feeding pressurized air51, and an air regulator 12 for regulating the air pressure to apredetermined value.

In the injection nozzle 15, the fuel from the injector 16 is injectedinto the pressurized air fed from the air pump 10 to establish a fuelmixed air 54, which will be then injected into the exhaust gas pipe 11by the nozzle 15. The excessive fuel will return from the fuel regulator17 to the tank 19 via a returning pipe 21.

The operation of the fourth embodiment will be explained below.

The pump 18 feeds the fuel 53 from the tank 19 in a pressurized mannerinto the fuel regulator 17 which in turn regulates the pressure of thefuel to a predetermined value and thereafter feeds the same into theinjector 16. The excessive fuel from the fuel regulator 17 returns tothe tank 19 via the return pipe 21.

The air pump 10 feeds air in a pressurized manner to the air regulator12 which in turn regulates the pressure of the air to a predeterminedvalue and thereafter feeds the same into the injection nozzle 15.

Into this pressurized air in the nozzle 15 is injected to be mixedtherewith the pressurized fuel by the injector 16 which has received thefuel in the above noted manner.

The injector 16 injectingly atomizes the fuel 53 into fine particleshaving diameters below 50μ.

As a result, into the exhaust gas within the exhaust pipe 11 isuniformly mixed with the mixture of fairly atomized fuel and pressurizedair, so that the vaporization of fuel is effectively promoted. The thusmixed exhaust gas is fed to the oxidation catalyst convertor 3, at whichthe exhaust gas is heated in the same manner with the third embodiment,and thereafter fed to the black smoke trapping filter 4 to burn theblack smoke as trapped thereby. The restoration of the filter 4 is thuscarried out.

FIG. 7 shows an exhaust gas cleaning system according to the fifthembodiment of the present invention.

In FIG. 7, the exhaust gas from the engine 1 is introduced into theblack smoke trapping filter 4 through the exhaust pipe 11 and heatingdevice 3. In this embodiment, the porous body 61 is provided in thedownstream of the filter 4 and has multiple small holes for cooling theexhaust gas. The temperature of exhaust gas in the downstream of theporous body 61 is detected by a temperature sensor 62.

The porous body 61 preferably consists of a heat-resistant ceramicmaterial, and there is adopted a cordierite ceramic foam having athickness of about 1 centimeter, in this embodiment.

The operation of the fifth embodiment is explained below.

The exhaust gas from the internal combustion engine 1 is heated by theheating device 3 and thereafter fed to the black smoke trapping filter 4to burn the black smoke as trapped thereby so as to attain therestoration of the filter 4.

The exhaust gas from the filter 4 passes through the porous body 61 tobe cooled thereby, and then exhausted into the atmosphere.

On this occasion, the latent heat of exhaust gas is absorbed by thesurfaces of the porous body 61 when passing therethrough, causing arapid descent of temperature of exhaust gas. The thus absorbed latentheat is backwardly radiated to the upstream of the porous body 61, as aradiant energy.

Consequently, there appear a field of high temperature and a field oflow temperature in the exhaust gas at the upstream and downstream of theporous body 61, respectively.

Thus, the exhaust gas at the downstream of the porous body 61 isexhausted into the exterior, with the descent width of temperature ofexhaust gas being typically as large as 50° C. to 100° C.

Shown in the diagram of FIG. 8 is such a temperature transition ordescent attained by the provision of the porous body 61. As apparenttherefrom, the fifth embodiment of the present invention provides such acooling effect that the temperature is higher and lower on the upstreamand downstream sides of the porous body 61, respectively, as compared tothe conventional effect.

FIG. 9 shows a temperature transition or descent of the exhaust gas inthe fifth embodiment in which is provided the porous body 61 (1centimeter thickness) made of cordierite ceramic foam at the downstreamof the black smoke trapping filter 4. As seen therefrom, this embodimentprovides such a cooling effect that the temperature of exhaust gas isdescended by as large as 50° C. to 100° C. as compared to theconventional effect in which no porous body is provided.

Referring again to FIG. 7, the temperature sensor 62 detects the exittemperature of exhaust gas and feeds a signal representative thereof toa controller (not shown) which controls actions of the system such asheating intensity of the heating device 3 and flow rate into the blacksmoke trapping filter 4, based on the thus fed signal.

The present invention is constituted in a manner as described above, sothat according to its first aspect, the means for introducing the fuelinto the exhaust gas and the oxidation catalyst for burning the fuelacting as a heating means are disposed at the upstream of the filter ina separated manner therefrom. Thus, there can be avoided thedeterioration of the oxidation catalyst due to heat of combustion ofblack smoke within the filter. Further, the temperature of filter iseffectively raised, leading to an increased quantitative reduction offuel consumption as well as shortening of time for raising temperature.

According to the second aspect of the present invention, there areattained uniformities of flow rates and temperatures of exhaust gasstreams into the plurality of heating devices and black smokeeliminating devices, respectively, by the provision of the baffle memberand space portion. Thus, the restoration of black smoke eliminatingdevice can be effectively carried out, whereby obtained is the blacksmoke eliminating device suitable for a large-sized engine having alarge displacement volume.

Further, according to the third and fourth aspects of the presentinvention, there is obtained a vertical flow of exhaust gas by means ofpartition plates of the fuel mixing device, so that the mixing of fuelwith exhaust gas is fully conducted. The black smoke eliminating deviceis therefore heated uniformly so that a partial restoration andoccurrence of melt damage thereof are avoided.

Moreover, according to the fifth to seventh aspects of the presentinvention, the fuel as atomized by fuel injection device into fairlyfine particles can be uniformly mixed into the exhaust gas. Accordingly,the heating of exhaust gas is performed uniformly and rapidly, so thatthe restoration of black smoke eliminating device by burnt eliminationof black smoke is effectively performed without failure.

Still further, according to the eighth aspect, there can be obtained thecooling effect for exhaust gas by such a very simple and compact meansof low cost that the porous body is straightforwardly provided at thedownstream of black smoke eliminating device, as comparative to thoseconventional large-sized and so expensive devices such as air-cooleddevices.

Although what have been described are at present considered to be thepreferred embodiments of the invention, it will be understood that thepresent invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription.

We claim:
 1. An exhaust gas cleaning system having a heating device forheating the exhaust gas from an internal combustion engine, and a blacksmoke eliminating device for eliminating the black smoke from theexhaust gas which is to be heated by said heating device comprising:aplurality of heating components in said heating device and a pluralityof filtering components in said eliminating device, said plurality ofcomponents in each of said heating and eliminating devices beingarranged in a parallel and divided manner perpendicularly to a flowdirection of the exhaust gas, so as to provide a divided type of heatingdevice and a divided type of black smoke eliminating device; a bafflemember disposed upstream of said divided type of heating device andbeing arranged to provide substantially uniform distribution of saidexhaust gas to said heating device; and a space portion defined at theupstream of said divided type of black smoke eliminating device of apredetermining volume sufficient to provide mixing of exhaust gasesheated by said divided type of heating device to substantially equalizethe temperature of said exhaust gases.
 2. An exhaust gas cleaning systemaccording to claim 1 wherein:said heating device comprises an oxidationcatalyst convertor; and said mixed fluid injection device is disposed onthe exhaust pipe at the upstream of said oxidation catalyst convertor.3. The exhaust gas cleaning system according to claim 1 wherein saidbaffle member comprises a substantially flat member positioneddiagonally with respect to said plurality of heating components arrangedin said parallel manner.
 4. The exhaust gas cleaning system according toclaim 2 wherein said baffle member comprises a substantially flat memberpositioned diagonally with respect to said plurality of heatingcomponents arranged in said parallel manner.
 5. An exhaust gas cleaningsystem having a heating device for heating the exhaust gas in an exhaustpipe from an internal combustion engine, and a black smoke eliminatingdevice for eliminating the black smoke from the exhaust gas which isheated by said heating device, said system further comprising:a fuelsupply device for supplying the fuel into the exhaust gas, said fuelsupply device being disposed on the exhaust pipe at the upstream of saidblack smoke eliminating device; and a fuel mixing device for mixing thefuel supplied from said supply device with the exhaust gas, said mixingdevice being disposed in the exhaust pipe at the upstream of said blacksmoke eliminating device, and said mixing device comprising a pluralityof substantially flat partition plates disposed along the exhaust gasflow at predetermined intervals and each of said partition plates beingformed with a through hole for passing therethrough the exhaust gas,said holes in said partition plates being shifted relative to each otherto form a turbulent flow thereof.
 6. An exhaust gas cleaning systemhaving the black smoke eliminating device according to claim 5wherein:said heating device comprises an oxidation catalyst convertor;and said fuel mixing device is disposed in the exhaust pipe at theupstream of said oxidation catalyst convertor.
 7. An exhaust gascleaning system exhaust pipe from an internal combustion engine, and ablack smoke eliminating device for eliminating the black smoke from theexhaust gas which is to be heated by said heating according to claim 3further comprising:a pressurized air supply device for supplyingpressurized air; a fuel injection device for injecting the fuel into thepressurized air to thereby atomize the fuel, said fuel injection devicebeing disposed on the exhaust pipe at the upstream of said black smokeeliminating device; and a mixed fluid injection device for mixing theinjected fuel with the pressurized air and for injecting the thus mixedfluid into the exhaust pipe, said fluid injection device being disposedon the exhaust pipe at the upstream of said black smoke eliminatingdevice.
 8. An exhaust gas cleaning system according to claim 6 or 7wherein said fuel injection device comprises:a fuel pump forpressurizing the fuel from a fuel tank and feeding the pressurized fuel;a fuel regulator for regulating the pressure of the pressurized fuel fedfrom said fuel pump; and an injector for injecting the pressurized fuelof a regulated flow rate from said regulator into the pressurized air.9. The exhaust gas cleaning system according to claim 5 wherein saidshifted holes in said partition plates are shifted circumferentiallywith respect to each other to promote vortical flow of the exhaust gascontaining fuel therein.